What’s up with the permanently blocked seats on the 757? I understand passenger weights went up, but wouldn’t the amount of baggage and cargo, fuel load and fuel burn, etc. make the number of seats necessary to block go up and down on each flight?

When I used to fly it from Europe to the US, they would sometimes cap the number of passengers to keep the weight, and therefore the fuel burn down (when the tanks were already full). But the number always varies.